SM8610CV Datasheet, PDF (6/9 Pages) Nippon Precision Circuits Inc – Laser Switching Driver IC

SM8610CV
FUNCTIONAL DESCRIPTION
LD Driver Control
The laser diode is controlled by 3 logic-level input signals: LDOFF, FLOCK, and MUTE. When LDOFF is
HIGH, the laser diode driver is ON, and the mode is controlled by FLCOK and MUTE. When LDOFF is LOW,
the laser diode drive is OFF and the IC is in power-save mode (LDIOUT output current = 0mA).
The LD has a chopper drive input when FLOCK is HIGH and MUTE is LOW.
Table 1. Laser diode control signals
LDOFF
H
H
H
H
L
Note) × : Don’t care.
FLOCK
L
L
H
H
×
MUTE
L
H
L
H
×
Laser drive state
LDIOUT constant-current output
LDIOUT constant-current output
LDIOUT chopper current output
LDIOUT constant-current output
LDIOUT = 0mA (power-save mode)
Pulsewidth Adjust and Frequency Multiplication Function
The SM8610CV internal waveform processor multiplies the PCK input signal frequency by 2, and the pulse-
width of this signal can be adjusted to control the duty ratio.
PCK
I(LDIOUT)
large current
a
b
duty ratio (a/b) control
The output pulse current (LD chopper signal) on LDIOUT is automatically adjusted to maintain roughly con-
stant duty ratio, even for changes in frequency. The LD chopper signal duty ratio can be adjusted by changing
the resistance R_DUTY connected between the DUTYADJ and GND pins, as given by the following equation.
dutyratio =
1−
3
2
V(DUTYADJ)
1
2
VCC(≈Vth)
× 100 =
22[kΩ] − 2 × RDUTY
RDUTY + 22[kΩ]
× 100 [%]
V(DUTYADJ) =
RDUTY
RDUTY + 22[kΩ]
× VCC [V]
R_DUTY : DUTYADJ connected resistance [kΩ]
NIPPON PRECISION CIRCUITS INC.—6